in the description of the Edge is stated that "...if his skill is lower than his controlling attribute, he can roll using the attribute value instead of the skill value..."
My interpretion is that you need at least a D4 in the skill in question ( to have an attribute value to compare) and no unskilled rolls are allowed.
Or am I wrong and even if you don`t have the associated skill you can roll the attribute value? And if that`s the case does the unskilled penalty (-2) applies to the roll ?